All Things D reports that Apple broke it down for them: The iPad displays that it is 100-percent charged before it is. At that point, it continues to charge to capacity, before dishcarging a little, and then charges back up to 100 percent again. Speaking to All Things D, Apple VP Michael Tchao explains:

"That circuitry is designed so you can keep your device plugged in as long as you would like. It's a great feature that's always been in iOS."

So while the tick has only surfaced now, it's apparently something we've in fact been living with for years. Tchao also reassures users that the percentage differences involved are small, so any difference has a minimal impact on battery life.

While it might sound like a cop-out, it's probably accurate. These days, batteries are complex things, which use microprocessors to control their charging. Back in the good ol'days, a charging analogy based on pouring ions into a cup was about right. These days, you probably need an electrical engineering degree to actually understand the process of charging a fancy battery. As Yankee Group analyst Carl Howe told All Things D:

"[W]e shouldn't apply our prejudices formed (both good and bad) from older generations of battery technology to today's systems... If it says it's charged, consumers should assume it is, and not worry about whether the charger is drawing current."